Nadal missed last year's edition during a seven-month injury break with knee trouble before making a stunning comeback to win 10 titles in 2013, including the French Open and US Open.

Now the rampant Spaniard will take aim at Djokovic's three-year reign at Melbourne Park, the longest of the Open era, and try to avenge his epic, six-hour loss to the Serb in the 2012 final.

He also arrives as the only "Big Four" player without a star coach, after Djokovic and Roger Federer, aping Andy Murray's move in hiring Ivan Lendl, hooked up with Boris Becker and Stefan Edberg respectively.

However, with Murray returning from injury and Federer now 32, the door could be open for a group of other contenders, led by Juan Martin del Potro and David Ferrer.

Nadal, still coached by his uncle, Toni Nadal, underwent a new but undisclosed form of treatment on his injury-prone knees in the off-season, and he appears confident he can stay healthy in 2014.

"I feel that this (treatment) really makes me feel more comfortable," he said in Doha, where he started his season by winning the Qatar Open.

Nadal's 2012 Melbourne appearance ended in the small hours and defeat to Djokovic following a Slam-record five-hour, 53-minute final, after which the Spaniard wished the crowd good morning.

In Nadal's absence last year, Djokovic showed similar powers of endurance when he ground down Murray in a physical four-setter to clinch his third straight Melbourne title.

It turned out to be the high point of Djokovic's year and after losing the Wimbledon and US Open finals, he ceded the top ranking to Nadal at the China Open in September.